Subacute thyroiditis is extremely rare during childhood. We treated a 10 year-old prepubertal girl who presented with typical clinical features of subacute thyroiditis. Considering this case and previous reports in children, we characterized the clinical features of this disorder as it occurs in childhood. In contrast to the predominance of subacute thyroiditis in adults, the incidence of subacute thyroiditis is lower than that of acute suppurative thyroiditis in children. This may cause difficulty with differential diagnosis, particularly when leukocytosis is present or the lesion is localized to the left lobe. Ultrasonography can be helpful in differentiation.